Spatial distribution and environmental characterization of sediment-associated metals from middle-downstream of Xiangjiang River, southern China

The contamination and environmental risk assessment of the toxic elements in sediments from the middle-downstream (Zhuzhou—Changsha section) of the Xiangjiang River in Hunan Province of China were studied. The results show that As, Cd, Pb and Zn are major contaminants in sediments, and average concentrations of these elements significantly exceed both the Control Standards for Pollutants in Sludge of China (GB4284-84) for agricultural use in acidic soils and the effect range median (ERM) values. The average concentrations of As, Cd and Pb in the river water slightly exceed the limit of Surface Water Environment Quality Standard (GB3838—2002). The concentrations of As and Cr in depth profiles extensively change, but slight changes are observed in Pb and Zn. Cd and Zn in most sediment samples can easily enter the food-chain and bring possible ecotoxicological risk to organisms living in sediments according to the risk assessment code.     

Aerobic biodegradation of di-n-butyl phthalate by Xiangjiang River sediment and microflora analysis

Di-n-butyl phthalate (DBP), one of phthalate acid esters (PAEs), was investigated to determine its biodegradation rate using Xiangjiang River sediment and find potential DBP degraders in the enrichment culture of the sediment. The sediment sample was incubated with an initial concentration of DBP of 100 mg/L for 5 d. The biodegradation rate of DBP was detected using HPLC and the degraded products were analyzed by GC/MS. Subsequently, the microbial diversity of the enrichment culture was analyzed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The results reveal that almost 100% of DBP is degraded after merely 3 d, generating two main degraded products: mono-butyl phthalate (MBP) and 9-octadecenoic acid. After a six-month enrichment period under the pressure of DBP, the dominant family in the final enrichment culture is clustered with the Comamonas sp., the remaining are affiliated with Sphingomonas sp., Hydrogenophaga sp., Rhizobium sp., and Acidovorax sp. The results show the potential of these bacteria to be used in the bioremediation of DBP in the environment.     

黄河宁夏段河道淤积发展趋势分析

对黄河宁夏段河道淤积因素进行了分析论述,根据实测水文资料和径流模型对现状条件下宁夏河道泥沙淤积发展趋势进行了预测分析：2011—2020年年平均来水量可能为260亿～280亿m^3;2011—2020年宁夏河段的淤积情况可能与1986--1995年淤积情况相近,主槽年淤积速率可能为0．02～0．03m,如若支流来沙量大则年均淤积速率将可能达到0．05m,甚至更大一些．     

ECOMSED三维悬沙扩散数值模型在凤城港航道清淤工程建设中的应用

文章用ECOMSED三维近岸水动力泥沙数学模型对山东烟台凤城港附近海区的潮流场进行了较高分辨率数值模拟,在此基础上进一步建立了凤城港航道清淤工程过程中三维悬沙输运-扩散数学模型。该模型以航道中心为悬沙线源,根据工程过程中连续开挖的特点较好的引入泥沙输入源强,准确地模拟了该航道中连续开挖36小时,工程区域及其周围海域表、中和底层泥沙浓度分布特征及其随时间的变化规律。     

水土保持措施对汾河水库泥沙淤积的影响

对山西省汾河水库1962～2008年淤积情况的分析结果表明:水库淤积量总体呈减小趋势。汛期降水量和来水量是造成水库淤积的主要原因,实施水土保持措施可减少水库淤积。     

Micro-computed tomography scanning approaches to quantify,parameterize and visualize bioturbation activity in clogged streambeds: A proof of concept

Fine particle clogging and faunal bioturbation are two key processes co-occurring in the hyporheic zone that potentially affect hyporheic exchange through modifications in the sediment structure of streambeds. Clogging results from excessive fine sediment infiltration and deposition in rivers, and it is known to decrease matrix porosity and potentially reduce permeability. Faunal bioturbation activity may compensate for the negative effect of clogging by reworking the sediment, increasing porosity, and preventing further infiltration of fines. Although both processes of clogging and bioturbation have received significant attention in the literature separately, their combined effects on streambed sediment structure are not well understood, mostly due to the lack of a standard methodology for their assessment. Here, we illustrate a novel methodology using X-ray computed tomography (CT), as proof of concept, to investigate how, together, clogging and bioturbation affect streambed porosity in a controlled flow-through flume. By visualising gallery formations of an upward conveyor macroinvertebrate; Lumbriculus variegatus as a model species, we quantified bioturbation activity in a clogged streambed, focusing on orientation, depth, and volume at downwelling and upwelling areas of the flume. Gallery creation increased the porosity of the streambed sediment, suggesting a potential improvement in permeability and a possible offset of clogging effects. We illustrate the promising use of X-ray CT as a tool to assess bioturbation in clogged streambeds, and the potential role of bioturbation activity supporting hyporheic exchange processes in streambeds, warranting further studies to understand the extent of bioturbation impacts in natural systems.     

Effect of the Three Gorges Reservoir on vertical distribution of suspended sediment concentration and estimation accuracy of depth-average concentration in downstream reaches

The sediment regime in the middle Yangtze River has been significantly changed from quasi-equilibrium to nonequilibrium since the impoundment of the Three Georges Reservoir (TGR). To understand the effects of the TGR on vertical distribution of suspended sediment concentration (SSC) and estimation accuracy of mean concentration, vertical sediment concentration and flow velocity data at the Shashi and Jianli hydrological stations in the reach before and after the impoundment were collected. Comparisons and analysis of vertical profiles of SSC before and after the TGR impoundment show that after the impoundment of the TGR, due to the coarsening of sediment particle size, the reduction in sediment load, and the significant decrease in sediment saturation, the vertical distribution of SSC in the downstream reaches became more uneven under medium and low water flows, which was reflected in the vertical gradient and the fluctuation degree of SSC significantly increased. In addition, the depth-average sediment concentrations were calculated by the selected-point method and the mean values calculated by the “multi-point method” were regarded as the “true mean” to evaluate the accuracy of the mean value calculated by the “few-point method.” It was found that the relative errors for the selected-point method were mainly positive before impoundment but mainly negative after impoundment. Additionally, the correction factors of one-point, two-point, and three-point methods and the position of the near-bed substituted point for the five-point method were given to reduce the error when the point measurements were used to calculate the depth-average sediment concentration in the downstream reaches.     

水库异重流的三维数值模拟及影响因素分析

不同水沙条件下异重流的潜入位置以及潜入后流速和含沙量的垂向分布规律是研究异重流运动规律的关键要素,对优化水库异重流的排沙调度、提高水库运用效益等至关重要。本文利用SCHISM三维水沙数学模型对水库异重流水槽试验进行了数值模拟,结果表明模型能够得到符合实际情况的垂线流速和含沙量分布,且异重流潜入后的平均厚度、平均流速和平均含沙量均与实测值吻合较好。对异重流模拟结果的分析发现,入口流量和含沙量的增加造成异重流运动速度越快,而入口含沙量的减小和流量的增加会造成异重流厚度增加。异重流垂向流速和含沙量的无量纲化分布受到入口水沙条件的影响,表现在其与断面Froude数的相关性,Froude数越大,则最大流速点与河床的距离越小,最大流速越大;含沙量致密层的厚度越小,对应的含沙量也越大。此外,潜入点位置也受入口水沙条件的影响,表现在潜入水深与入口水深之比随入口Froude数增加而增加的定量关系,由此可以利用入口水沙条件预报异重流潜入的位置。研究结果不仅验证了SCHISM模型用于模拟水库异重流运动的优势,而且丰富和完善了关于异重流潜入点位置及流速和含沙量垂向分布受入口水沙条件影响的变化规律。     

黄河水滴灌系统灌水器结构-泥沙淤积-堵塞行为的相关关系研究

传统的黄河水沉淀-过滤系统存在沉沙池建设成本高、过滤器频繁反冲洗能耗高等问题,让更多的细颗粒泥沙随水流排出灌水器体外是解决黄河水滴灌系统灌水器堵塞的新思路,而摸清泥沙在黄河水滴灌系统内部的淤积特性以及灌水器结构-淤积泥沙特性-堵塞特性参数间的相关关系是探索其排沙能力的前提和基础。为此,本文在河套灌区开展了黄河水滴灌系统灌水器堵塞原位试验,系统分析了6种内镶贴片式灌水器内部细颗粒泥沙含量及粒径分布动态变化特征,探索了三者间的级联关系。结果表明：进入灌水器内部的泥沙99%以上可以排出体外,淤积在灌水器内部的泥沙以粉粒为主、砂粒次之、黏粒最少。随着灌水器堵塞加剧,内部淤积泥沙的黏粒、粉粒比例相对降低,而砂粒比例相对增加,泥沙进入灌水器后存在聚集等行为,使得灌水器内部淤积泥沙粒径明显高于毛管入口。泥沙比表面积淤积量、粉粒比例、砂粒比例、D₅₀、D₉₅对黄河水滴灌系统Dra、克里斯琴森均匀系数CU影响显著（p<0.05）,不同灌水器淤积泥沙粒径明显不同,D₅₀与灌水器结构无量纲参数（流道宽深比W/D、面积长度比A^1/2/L）及断面平均流速v显著（p<0.05）相关。本研究对引黄滴灌灌水器设计及灌溉系统过滤配置具有指导意义。     

有压输沙管道脉动压强特性试验研究

壁面脉动压强是工程上重要的研究对象,脉动强度直接影响泄洪排沙洞、输水隧洞(管道)等建筑物的稳定性和运行安全。为研究不同含沙浓度对壁面脉动压强特性的影响,以黄河细沙(d50=107μm)为研究对象,在直径80 mm的水平管道中进行模型试验,测量出每种工况下的流量、含沙浓度和脉动压强。采用统计方法对测量数据进行多方面分析,并结合快速傅里叶变换(FFT)方法研究了脉动压强的功率谱密度。试验结果表明,时均压强的沿程幅值和瞬时峰值压强均随含沙浓度增加而增大,相对脉动强度随着含沙浓度增大总趋势是减小的;脉动压强概率密度为脉动压强均值接近于零的正太分布,随着含沙浓度增加分布形态从瘦高型发展成矮胖型,压强振幅变大;脉动压强功率谱密度中低频分量随着含沙浓度变大有明显的增加。